Someone left a human heart on a Southwest Airlines flight

Passengers on a Southwest flight from Seattle to Dallas got more drama than they bargained for on Sunday when their plane was forced to turn around and return to Seattle. It was discovered that a human heart, intended as a transplant, had been left on board. 

The plane had made it close to the border of Idaho and Wyoming when the decision was made to turn around and return the heart to Seattle, according to an account in the Seattle Times.

In an email statement to Mashable, Southwest Airlines said:

One big problem, though: a heart transplant must happen almost immediately. According to the Columbia University Irving Medical Center, a heart can only be stored for between four and six hours for a transplant. 

SEE ALSO: All-female aircraft repair team is set on changing the industry

The heart first boarded the plane in Sacramento, according to a spokesperson for Southwest. A nonstop flight between the cities can take close to two hours. It's unclear how long the flight was in the air before it made its return to Seattle or if the heart was intended for a specific patient. None of the hospitals contacted by the Times said they were awaiting a transplant.

Dr. Andrew Gottschalk, a passenger on the flight with no connection to the heart onboard, told the Times the odyssey was a “horrific story of gross negligence."

According to the U.S. Department of Health and Human Services, there are an average of 20 patients each day awaiting an organ transplant. 

We have reached out to Southwest Airlines for additional comments, and we'll update this post if we hear back. 

WATCH: These drones can open doors and let the rest of the swarm in